1. Technical Field
The present invention relates to a novel composition for forming underlayer coating for lithography, an underlayer coating formed from the composition and a method for forming photoresist pattern by use of the underlayer coating. In addition, the present invention relates to an underlayer coating for lithography that can be used for an underlayer anti-reflective coating for reducing reflection of exposure irradiation light from a semiconductor substrate to a photoresist layer formed on the substrate in a lithography process of the manufacture of semiconductor devices, a flattening coating for flattening a semiconductor substrate having unevenness, a coating for preventing contamination of a photoresist layer due to substances generated from a semiconductor substrate on baking under heating, and the like; a composition for forming the underlayer coating, and a method for forming the underlayer coating. Further, the present invention relates to a composition for forming underlayer coating for lithography that can be used for filling holes formed on a semiconductor substrate.
2. Background Art
Conventionally, in the manufacture of semiconductor devices, micro-processing by lithography using a photoresist has been carried out. The micro-processing is a processing method comprising forming a thin film of a photoresist on a semiconductor substrate such as a silicon wafer, irradiating actinic rays such as ultraviolet rays through a mask pattern on which a pattern for a semiconductor device is depicted, developing it to obtain a photoresist pattern, and etching the substrate using the photoresist pattern as a protective film, thereby forming fine unevenness corresponding to the pattern on the surface of the substrate. However, in recent progress in high integration of semiconductor devices, there has been a tendency that shorter wavelength actinic rays are being used, i.e., ArF excimer laser beam (193 nm) has been taking the place of KrF excimer laser beam (248 nm). Along with this change, influences of random reflection and standing wave of a substrate have become serious problems. Accordingly, it has been widely studied to provide an anti-reflective coating between the photoresist and the substrate (Bottom Anti-Reflective Coating, BARC) in order to resolve the problem. As the anti-reflective coating, from a viewpoint of easy of use, many considerations have been done on organic anti-reflective coatings made of a light absorbing substance and a polymer compound and the like. For example, mention may be made of the acrylic resin type anti-reflective coating having a hydroxyl group being a crosslinking reaction group and a light absorbing group in the same molecule and the novolak resin type anti-reflective coating having a hydroxyl group being a crosslinking reaction group and a light absorbing group in the same molecule (see, for example U.S. Pat. Nos. 5,919,599 and 5,693,691).
The physical properties desired for organic anti-reflective coating include high absorbance to light and radioactive rays, no intermixing with the photoresist layer (being insoluble in photoresist solvents), no diffusion of low molecular substances from the anti-reflective coating into the topcoat photoresist upon baking under heating, and a higher dry etching rate than the photoresist (see, for example, Tom Lynch et al., “Properties and Performance of Near UV Reflectivity Control Layers”, US, in Advances in Resist Technology and Processing XI, Omkaram Nalamasu ed., Proceedings of SPIE, 1994, Vol. 2195, p. 225-229; G. Taylor et al., “Methacrylate Resist and Antireflective Coatings for 193 nm Lithography”, US, in Microlithography 1999: in Advances in Resist Technology and Processing XVI, Will Conley ed., Proceedings of SPIE, 1999, Vol. 3678, p. 174-185; and Jim D. Meador et al., “Recent Progress in 193 nm Antireflective Coatings, US, in Microlithography 1999: in Advances in Resist Technology and Processing XVI, Will Conley ed., Proceedings of SPIE, 1999, Vol. 3678, p. 800-809).
In recent years, in order to solve interconnection delay that has become clear with miniaturization in pattern rule of semiconductor devices, it has been considered to use copper as interconnect material, and to apply Dual Damascene process as interconnect forming method on the semiconductor device. And, in Dual Damascene process, via holes are formed and an anti-reflective coating is formed on a substrate having a high aspect ratio. Therefore, the anti-reflective coating for use in this process is required to have filling property by which holes can be filled without gap, flattening property by which a flat coating can be formed on the surface of substrate, and the like.
However, it is difficult to apply organic material for anti-reflective coating on a substrate having a high aspect ratio, and in recent years, material with particular emphasis on filling property or flattening property has been developed (see, for example JP 2000-294504 A, JP 2002-47430 A, JP 2002-190519 A and WO 02/05035 pamphlet,).
In addition, in the production of devices such as semiconductors, in order to reduce poisoning effect of a photoresist layer induced by a dielectric layer, there is disclosed a method in which a barrier layer formed from a composition containing a crosslinkable polymer and the like is provided between the dielectric layer and the photoresist layer (see, for example JP 2002-128847 A).
As mentioned above, in the recent manufacture of semiconductor devices, in order to attain several effects represented by anti-reflective effect, it comes to provide an organic underlayer coating formed from a composition containing an organic compound between a semiconductor substrate and a photoresist layer, that is, as an underlayer of the photoresist.
As the underlayer coating is required to cause no intermixing, a crosslinking reaction is utilized for the formation of the underlayer coating in many cases. And, as the composition for forming such a crosslinkable underlayer coating, a composition comprising a polymer, a crosslinking agent and a sulfonic acid compound as a crosslinking catalyst is used (see, for example U.S. Pat. No. 5,919,599, JP 2000-294504, JP Patent 2002-47430 and WO 02/05035 pamphlet). However, as the compositions contain a strong acid being the sulfonic acid compound, they are anticipated to have a problem in shelf stability.
Therefore, an underlayer coating formed by use of crosslinking reaction for which no strong acid catalyst is required, and a composition therefor are desired.
In the meanwhile, it is known a technique in which tris(hydroxyalkyl) isocyanurate substituted with an aromatic compound or a an alicyclic compound is used as a broad ultraviolet light absorber (see, for example JP 11-279523 A), and an anti-reflective coating forming composition containing a cyanuric acid compound (see, for example WO 02/86624 pamphlet).
Taking the above-mentioned present status into account, the present inventors have eagerly studied, and as a result of it, found that the use of a compound having an epoxy group (a polymer compound) and a compound having a phenolic hydroxy group, a carboxyl group, a protected carboxyl group or an acid anhydride structure (a polymer compound) makes possible to form an underlayer coating by use of crosslinking reaction for which a strong acid catalyst such as a sulfonic acid compound and the like is not required, and they completed the present invention.
That is, an object of the present invention is to provide a composition for forming underlayer coating that can be used for the production of semiconductor devices, and to provide an underlayer coating for lithography that causes no intermixing with a photoresist applied and formed as an upper layer and that has a high dry etching rate compared with the photoresist, and an underlayer coating forming composition for forming the underlayer coating. Further, another object of the present invention is to provide an underlayer coating formed by use of crosslinking reaction for which no strong acid catalyst is required, a method for forming the underlayer coating and an underlayer coating forming composition therefor.
Further, an object of the present invention is to provide an underlayer coating for lithography that can be used for an underlayer anti-reflective coating for reducing reflection of exposure irradiation light from a semiconductor substrate to a photoresist layer formed on the substrate in a lithography process of the manufacture of semiconductor devices, a flattening coating for flattening a semiconductor substrate having unevenness, a coating for preventing contamination of a photoresist layer due to substances generated from a semiconductor substrate on baking under heating; a composition for forming the underlayer coating. And another object of the present invention is to provide a method for forming underlayer coating for lithography by use of the underlayer coating forming composition, and a method for forming a photoresist pattern.